Autism (AW-tiz-um) is a complex developmental disability that's the result of a brain disorder. It typically appears in children during the first three years, more often in boys than girls, and can continue into adulthood.

Chicken pox, whose technical name is 'varicella' (var-uh-SELL-uh), is a common, highly-contagious disease usually contracted during childhood. Parents often deliberately expose their young children to chicken pox, so the children won't have it as adults, when it can be serious.

Diaper rash is an inflamed, red rash on a baby's buttocks, thighs, and genitals. It's usually a mild bacterial infection, but it also can be an allergic reaction to detergent the diaper was washed in or to a chemical or material used in a disposable diaper.

'Down's syndrome' is the name of a birth defect that occurs in about one in every 800 babies. It's caused by the presence of three chromosome-21s in the nucleus of the child's cells, rather than the normal two.

Fever is usually a sign that the body is trying to fight off an infection or other illness. In a child, however, even if the body temperature is above or below an adult's normal temperature of 98-point-six degrees, it's not necessarily an indication that the child's sick.

Many children, especially preschool children, are said to be 'hyperactive.' However, that term may be misused to describe a child who's merely active and busy, which is a normal part of being a child and not necessarily a disorder.

Children's sleep patterns vary between birth and age 12. The amount of sleep a child needs depends on the individual child, with some children requiring more or less sleep than others, and that amount changes as the child gets older.

Reye's (RIZE) syndrome is a potentially fatal disease of the brain and liver. Ralph Douglas Reye (RYE) was an Australian pathologist who first described the syndrome in young children, and the condition soon after became known as 'Reye's syndrome.

Ringworm is a common and easily-treated skin infection. Many years ago, it was believed to be caused by a worm present under the skin, but it's now known that the circular-shaped lesions-- hence, the name-- are the body's response to a fungus.

Many children are reluctant to go to bed, or they have problems once they're in bed. Some of these can include difficulty falling asleep, awakening during the night, talking during sleep, nightmares, or bed-wetting.

Vaccinations are an important way you can help your child avoid illnesses throughout life, many of which were unavoidable only a few years ago. Even diseases that used to be common in childhood-- such as polio, measles, and mumps--now have been practically eliminated, thanks to vaccines.

Most children begin to stay dry at night around three years of age. However, bed-wetting, whose medical name is 'enuresis' (en-yoo-REE-sis), can be a problem for some children, even after they've been toilet trained.